MySQL语句练习

2019-11-06 06:52:54

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1、Table: Person

Write a SQL query for a report that provides the following information for each person in the Person table, regardless if there is an address for each of those people: FirstName, LastName, City, State

考察知识点：外联结，TableA LEFT JOIN TableB ON 联结条件答案：

select FirstName,LastName,City,Statefrom Person left join Addresson Person.PersonId = Address.PersonId;

2、Write a SQL query to get the second highest salary from the Employee table.

+—-+——–+ | Id | Salary | +—-+——–+ | 1 | 100 | | 2 | 200 | | 3 | 300 | +—-+——–+ For example, given the above Employee table, the second highest salary is 200. If there is no second highest salary, then the query should return null.

考察知识点：排序、限制输出行数：LIMIT m OFFSET n,从第n行开始取最多不超过m行数据（注意是从第0行开始数的）答案：

select ( select distinct Salary from Employee order by Salary desc limit 1 offset 1) as SecondHighestSalary;

3、Write a SQL query to rank scores. If there is a tie between two scores, both should have the same ranking. Note that after a tie, the next ranking number should be the next consecutive integer value. In other Words, there should be no “holes” between ranks.

+—-+——-+ | Id | Score | +—-+——-+ | 1 | 3.50 | | 2 | 3.65 | | 3 | 4.00 | | 4 | 3.85 | | 5 | 4.00 | | 6 | 3.65 | +—-+——-+ For example, given the above Scores table, your query should generate the following report (order by highest score):

+——-+——+ | Score | Rank | +——-+——+ | 4.00 | 1 | | 4.00 | 1 | | 3.85 | 2 | | 3.65 | 3 | | 3.65 | 3 | | 3.50 | 4 | +——-+——+ 思路：先找到每个成绩的排名，然后再倒序输出成绩和该成绩的排名答案：

select Score, (select count(*) from (select distinct Score as s from Scores) as temp where s > Score) as Rankfrom Scores order by Score desc;

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